Roller Tube

ABSTRACT

The present invention is a roller tube for rolling up a fabric blind. The roller tube consists of an elongated tube having a length, an inner surface and an outer surface. An elongated lip is formed on the outer surface of the elongated tube and extends along the entire length of the elongated tube. The lip has a height substantially equal to the thickness of the fabric blind which is to be wound onto the roller tube. The outer surface of the elongated tube has a first cross sectional diameter at the lip and a second cross sectional diameter at an angle from the first cross sectional diameter, the first cross sectional diameter being larger than the second cross sectional diameter by the height. The inner surface of the elongated tube has a circular profile. A notch is formed on the inner surface of the elongated tube adjacent the lip, said notch extending along the length of the elongated tube. The notch and lip are parallel to the axis of the roller tube.

FIELD OF THE INVENTION

The invention relates generally to roller tubes as used in roller blindsto roll up a fabric blind.

BACKGROUND OF THE INVENTION

Roller blinds generally consist of a fabric blind which is rolled ontoan elongated cylindrical roller tube. The roller tube is coupled to somesort of clutch mechanism which operates to rotate the roller tube aboutits axis in order to roll up or roll down the fabric blind mounted tothe roller tube. The fabric blind has one end affixed to the rollertube, usually by a length of adhesive tape. As the roller tube isrotated, the fabric blind is wound (i.e. rolled up) onto the rollertube. Since one end of the blind is attached to the roller tube by alength of adhesive tape, and since the roller tube has a circular crosssectional profile, the fabric does not maintain a circular crosssectional profile as it is wound onto the tube. Rather, it is moreaccurate to say that the fabric is oriented in a spiral fashion onto theroller tube, with one side of the wound fabric being slightly thickerthan the other side.

Assembling a roller tube by attaching one end of the fabric blind to thetube is time consuming because the end of the fabric must be maintainedperfectly parallel to the axis of the roller tube, otherwise the blindcannot be properly wound onto the roller tube. Therefore, assembling aroller blind takes a surprisingly long time. A guide line drawn on thetube may provide some assistance when aligning the end of the blind tothe tube, but it is very easy to misalign the end of the fabric blindwith a guide line during the securing process. An improved roller tubewhich permits the quick and accurate attachment of the fabric blind tothe tube is therefore required.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided an improved roller tube for rolling up a fabric blind whichovercomes the drawbacks of the prior art. In particular, a rolle tubemade in accordance with the present invention includes an elongated tubehaving a length, an inner surface and an outer surface. An elongated lipis formed on the outer surface of the elongated roller tube and extendsalong the length of the elongated tube. The lip has a heightsubstantially equal to the thickness of the fabric blind. The outersurface has a first cross sectional diameter at the lip and a secondcross sectional diameter at an angle from the first cross sectionaldiameter, the first cross sectional diameter being larger than thesecond cross sectional diameter by the height. The inner surface of theelongated tube has a circular profile. A notch is formed on the innersurface of the elongated tube adjacent the lip, the notch extendingalong the length of the elongated tube.

With the foregoing in view, and other advantages as will become apparentto those skilled in the art to which this invention relates as thisspecification proceeds, the invention is herein described by referenceto the accompanying drawings forming a part hereof, which includes adescription of the preferred typical embodiment of the principles of thepresent invention.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a roller tube made in accordancewith the present invention.

FIG. 2 is a close up of the lip portion of the roller tube shown in FIG.1.

FIG. 3 is a perspective view of part of a blind rolled on a roller tubemade in accordance with the present invention.

FIG. 4 is an exploded view of a roller blind made with the roller tubeof the present invention.

In the drawings like characters of reference indicate correspondingparts in the different figures.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1 and 2, a roller tube made in accordance with thepresent invention is shown generally as item 10 and includes anelongated roughly cylindrical tube 12 having an outer surface 14 and aninner surface 16. Tube 12 preferably consists of an extruded aluminumtube. Lip 18 is formed on outer surface 14 of tube 12 and notch 20 isformed on inner surface 16 adjacent lip 18. Lip 18 has a wall 28 with anupper rim 26. Wall 28 has a height 30 which is selected to besubstantially equal to the thickness of fabric blind 24. Lip 18 isexactly parallel to central axis 22 of roller tube 10.

Roller tube 10 has a cross sectional profile which is not perfectlycircular. In particular, roller tube 10 has an external diameter whichis different depending on where the diameter is measured, due to theheight of wall 28 of lip 18. The external diameter of tube 10 taken atlip 18, which is indicated by dotted line 32 is slightly greater thanthe external diameter of tube 10 taken adjacent to lip 18 which isindicated by dotted line 34. Diameters 32 and 34 are separated by angleα. The internal diameter of tube 10, indicated by dotted line 36 isidentical regardless of where the internal diameter is measured. Thethickness of tube wall 13 very gradually changes relative to angle α,with the thickness of the wall being greatest at lip 18 (as indicated bydotted line 32) and thinnest at a point immediately counter clockwise(as viewed in FIG. 1) to lip 18 indicated by dotted line 34. Hence,difference in the thickness of wall 13 is equal to height 30. Thestructure of tube 10 can be made by machining a regular cylindricalaluminum tube, or more preferably, by creating a separate extrusion withthe profile formed in the extrusion die. The desired effect is ablind/roller tube combination which, when end 25 of blind fabric 24 isattached at lip 18, will have an exactly circular combined cross sectionrather than a raised bump where the blind contacts the roller tube.

Notch 20 is positioned adjacent lip 18. Preferably, notch 20 ispositioned away from notch 20 by a distance 38. Distance 38 is selectedsuch that tube wall 13 will not be too thin immediately adjacent notch20. Preferably, tube wall 13 should have a thickness of at least about1.7 mm depending on the desired dimensions of the tube. Distance 38should preferably be at least 1.7 mm to ensure that tube wall 13 is atleast 1.7 mm thick between notch 20 and lip 18. Notch 20 acts as anattachment point for a clutch member and idle end (see FIG. 4).

Referring now to FIG. 4, roller tube 10 is used in conjunction withclutch motor 40, idler end 42, blind 24 and brackets 44 and 46 to form aroller blind. The internal notch in roller tube 10 provides anattachment point for clutch motor 40 and idle end 42. As shall bedescribed below, the lip formed on the roller tube also ensures thatblind 24 is properly aligned relative to roller tube 10.

Referring now to FIG. 3, lip 18 provides a very convenient means forproperly aligning end 25 of blind 24 onto roller tube 10. In particular,lip 18, being the same thickness as fabric blind 24 acts as a wall whichpermits end 25 of the fabric blind to be butted against. Since lip 18 isexactly parallel to axis 22, lip 18 provides a physical alignment meansfor keeping end 25 of the fabric blind in alignment with axis 22. Thismakes the assembly of the blind quicker and easier. In addition, whenblind 24 is attached as illustrated in FIG. 3, the blind willeffectively maintain a circular cross section as the blind is wound ontothe roller tube because the height of lip 18 is substantially equal tothe thickness of the fabric forming blind 24.

A specific embodiment of the present invention has been disclosed;however, several variations of the disclosed embodiment could beenvisioned as within the scope of this invention. It is to be understoodthat the present invention is not limited to the embodiments describedabove, but encompasses any and all embodiments within the scope of thefollowing claims.

1. A roller tube for rolling up a fabric blind, the roller tubecomprising: an elongated tube having a length, an inner surface and anouter surface; an elongated lip formed on the outer surface of theelongated roller tube and extending along the length of the elongatedtube, the lip having a height substantially equal to a thickness of thefabric blind; the outer surface having a first cross sectional diameterat the lip and a second cross sectional diameter at an angle from thefirst cross sectional diameter, the first cross sectional diameter beinglarger than the second cross sectional diameter by the height; the innersurface of the elongated tube having a circular profile; a notch beingformed on the inner surface of the elongated tube adjacent the lip, saidnotch extending along the length of the elongated tube.
 2. The rollertube as defined in claim 1 wherein the notch and the lip are parallel.3. The roller tube as defined in claim 1 wherein the tube has an axisand wherein the lip and groove are parallel to the axis.
 4. The rollertube as defined in claim 1 wherein the notch is at least 1.7 mm from thelip.